A347875 Numbers k such that A323905(sigma(k)) is equal to A323905(2*k).

1, 6, 21, 28, 496, 8128

Offset: 1

Author

Antti Karttunen, Sep 19 2021

Keywords

• nonn
• more

Comments

Numbers k such that A323905(sigma(k)) = A332221(k) - A331750(k) is equal to 2*A156552(k) - A048675(k) = A156552(k) + A323905(k).

Links

• Index entries for sequences where odd perfect numbers must occur, if they exist at all

Crossrefs

Cf. A000203, A048675, A156552, A323905, A347876.

Cf. also A000396 (subsequence), A331751, A347392.

Programs

PARI

A048675(n) = { my(f = factor(n)); sum(k=1, #f~, f[k, 2]*2^primepi(f[k, 1]))/2; }; \\ From A048675
A156552(n) = {my(f = factor(n), p, p2 = 1, res = 0); for(i = 1, #f~, p = 1 << (primepi(f[i, 1]) - 1); res += (p * p2 * (2^(f[i, 2]) - 1)); p2 <<= f[i, 2]); res}; \\ From A156552
A323905(n) = (A156552(n) - A048675(n));
isA347875(n) = (A323905(sigma(n))==A323905(2*n));